Sizing composition for mineral wool comprising a reducing sugar and an inorganic acid metal salt, and insulating products obtained

ABSTRACT

The present invention relates to a sizing composition for insulating products based on mineral wool, in particular of glass or of rock, which comprises:
     at least one reducing sugar, and   at least one inorganic acid metal salt chosen from inorganic acid alkali metal, alkaline earth metal, transition metal or poor metal salts.   

     Another subject matter of the present invention is the insulating products based on mineral fibers obtained and their process of manufacture.

The present invention relates to the field of thermal and/or acousticinsulating products based on mineral wool, in particular of glass or ofrock, and on a formaldehyde-free binder.

The invention more particularly relates to a sizing composition capableof crosslinking to form said binder, which includes at least onereducing sugar and at least one inorganic acid metal salt, to theprocess for the manufacture of thermal and/or acoustic insulatingproducts and to the insulating products which result therefrom.

The manufacture of insulating products based on mineral wool generallycomprises a stage of manufacture of the wool itself, which can becarried out by various processes, for example according to the knowntechnique of fiberizing by internal or external centrifugation.

Internal centrifugation consists in introducing the molten material(generally glass or a rock) into a centrifugal device comprising amultitude of small orifices, the material being projected toward theperipheral wall of the device under the action of the centrifugal forceand escaping therefrom in the form of filaments. On leaving thecentrifugal device, the filaments are drawn and carried toward areceiving member by a gas stream having a high temperature and a highspeed, in order to form a web of fibers (or mineral wool).

External centrifugation consists, for its part, in pouring out themolten material at the external peripheral surface of rotating members,known as rotors, from where the melt is ejected under the action of thecentrifugal force. Means for drawing by gas stream and for collecting ona receiving member are also provided.

In order to provide for the assembly of the fibers together and to makeit possible for the web to have cohesion, a sizing compositioncomprising a thermosetting resin is projected onto the fibers, on theroute between the outlet of the centrifugal device and the receivingmember. The web of fibers coated with the size is subjected to a heattreatment, at a temperature generally of greater than 100° C., in orderto bring about the polycondensation of the resin and to thus obtain athermal and/or acoustic insulating product having specific properties,in particular dimensional stability, tensile strength, thicknessrecovery after compression and homogeneous color.

The sizing composition to be projected onto the mineral wool isgenerally provided in the form of an aqueous solution including thethermosetting resin and additives, such as a catalyst for thecrosslinking of the resin, an adhesion-promoting silane, adust-preventing mineral oil, and the like. The sizing composition isgenerally applied to the fibers by spraying.

The properties of the sizing composition depend largely on thecharacteristics of the resin. From the viewpoint of the application, itis necessary for the sizing composition to exhibit good sprayability andto be able to be deposited at the surface of the fibers in order toefficiently bind them.

The resin has to be stable for a given period of time before being usedto form the sizing composition, which composition is generally preparedat the time of use by mixing the resin and the additives mentionedabove.

At the regulatory level, it is necessary for the resin to be regarded asnon-polluting, that is to say for it to comprise—and for it to generateduring the sizing stage or subsequently—as little as possible in the wayof compounds which may be harmful to human health or to the environment.

The thermosetting resins most commonly used are phenolic resinsbelonging to the family of the resols. In addition to their goodcrosslinkability under the abovementioned thermal conditions, theseresins are soluble in water, have a good affinity for mineral fibers, inparticular glass fibers, and are relatively inexpensive.

These resols are obtained by condensation of phenol and formaldehyde, inthe presence of a basic catalyst, in a formaldehyde/phenol molar ratioof greater than 1, so as to promote the reaction between the phenol andthe formaldehyde and to reduce the level of residual phenol in theresin. The condensation reaction between the phenol and the formaldehydeis carried out while limiting the degree of condensation of themonomers, in order to avoid the formation of long, relativelywater-insoluble, chains which reduce the dilutability. Consequently, theresin comprises a certain proportion of unreacted monomer, in particularformaldehyde, the presence of which is undesirable because of its knownharmful effects.

For this reason, resol-based resins are generally treated with urea,which reacts with the free formaldehyde by trapping it in the form ofnonvolatile urea-formaldehyde condensates. The presence of urea in theresin in addition brings a certain economic advantage as a result of itslow cost because it is possible to introduce it in a relatively largeamount without affecting the operating qualities of the resin, inparticular without harming the mechanical properties of the finalproduct, which significantly lowers the total cost of the resin.

Nevertheless, it has been observed that, under the temperatureconditions to which the web is subjected in order to obtain crosslinkingof the resin, the urea-formaldehyde condensates are not stable; theydecompose with restoration of the formaldehyde and urea, in its turn atleast partially decomposed to give ammonia, which are released into theatmosphere of the factory.

Regulations with regard to environmental protection, which are becomingmore restrictive, are forcing manufacturers of insulating products tolook for solutions which make it possible to further lower the levels ofundesirable emissions, in particular of formaldehyde.

Solutions in which resols are replaced in sizing compositions are known.

A first solution is based on the use of a carboxylic acid polymer, inparticular an acrylic acid polymer.

In U.S. Pat. No. 5,340,868, the size comprises a polycarboxylic polymer,a β-hydroxyamide and an at least trifunctional monomeric carboxylicacid.

Other sizing compositions have been provided which comprise apolycarboxylic polymer, a polyol and a catalyst, this catalyst beingable to be a phosphorus-comprising compound (U.S. Pat. No. 5,318,990,U.S. Pat. No. 5,661,213, U.S. Pat. No. 6,331,350, US 2003/0008978), afluoroborate (U.S. Pat. No. 5,977,232) or else a cyanamide, adicyanamide or a cyanoguanidine (U.S. Pat. No. 5,932,689).

The sizing compositions based on a polycarboxylic polymer and on apolyol can additionally comprise a cationic, amphoteric or nonionicsurfactant (US 2002/0188055), a coupling agent of silane type (US2004/0002567) or a dextrin as cobinder (US 2005/0215153).

A description has also been given of sizing compositions comprising analkanolamine including at least two hydroxyl groups and a polycarboxylicpolymer (U.S. Pat. No. 6,071,994, U.S. Pat. No. 6,099,773, U.S. Pat. No.6,146,746) in combination with a copolymer (U.S. Pat. No. 6,299,936).

A second solution in which resols are replaced is based on thecombination of a saccharide and a polycarboxylic acid.

In U.S. Pat. No. 5,895,804, a description is given of an adhesivecomposition based on heat-crosslinkable polysaccharides which can beused as size for mineral wool. The combination includes a polycarboxylicpolymer having at least two carboxylic acid functional groups and amolecular weight at least equal to 1000, and a polysaccharide having amolecular weight at least equal to 10 000.

In WO 2009/080938, the sizing composition comprises a monosaccharideand/or a polysaccharide and an organic polycarboxylic acid with a molarmass of less than 1000.

A formaldehyde-free aqueous sizing composition which comprises aMaillard reaction product, in particular combining a reducing sugar, acarboxylic acid and aqueous ammonia (WO 2007/014236), is also known. InWO 2009/019232 and WO 2009/019235, the proposal is made to substitute,for the carboxylic acid, an acid precursor derived from an inorganicsalt, in particular an ammonium salt, which exhibits the additionaladvantage of being able to replace all or part of the aqueous ammonia.

The latter sizing compositions nevertheless comprise nitrogen-includingcompounds which are capable of decomposing, in particular to giveammonia, during the heat treatment employed in order for the mineralfibers to be able to be bonded to one another and to form the finalinsulating product.

An aim of the present invention is to provide a sizing composition forinsulating products based on mineral wool, in particular of glass or ofrock, which is devoid of formaldehyde and other nitrogenous compounds.

In order to achieve this aim, the present invention provides a sizingcomposition which comprises:

-   at least reducing sugar, and-   at least one inorganic acid metal salt chosen from inorganic acid    alkali metal, alkaline earth metal, transition metal or poor metal    salts.

The reducing sugar in accordance with the present invention is amonosaccharide, an oligosaccharide, a polysaccharide or a mixture ofthese compounds.

Mention may be made, as example of monosaccharide, of glucose,galactose, mannose and fructose.

The term “oligosaccharide” is understood to mean a saccharide includingfrom 2 to 10 saccharide units, preferably at most 5.

Mention may be made, as example of oligosaccharide, of lactose, maltose,isomaltose and cellobiose.

The polysaccharides in accordance with the invention are chosen from thepolysaccharides having a number-average molar mass of less 100 000,preferably of less than 50 000 and advantageously of less than 10 000.

Mention may be made, as example of preferred polysaccharide, ofdextrins. Dextrins are compounds corresponding to the general formula(C₆H₁₀O₅)_(n) obtained by partial hydrolysis of starch. The processesfor the preparation of dextrins are known. For example, dextrins can beprepared by heating or by drying to dryness a starch, generally in thepresence of an acid catalyst, which results in the constituent amyloseand amylopectin molecules of said starch being ruptured to give productsof lower molar mass. Dextrins can also be obtained by treating thestarch enzymatically with one or more amylases, in particular microbialamylases, capable of hydrolyzing the bonds of the starch. The nature ofthe treatment (chemical or enzymatic) and the hydrolysis conditions havea direct effect on the average molar mass and the distribution of themolar masses of the dextrin.

The dextrins according to the present invention exhibit a dextroseequivalent (DE) of greater than or equal to 5, preferably of greaterthan or equal to 15.

Conventionally, the dextrose equivalent DE is defined by the followingrelationship:

${DE} = {100 \times \left( \frac{{number}\mspace{14mu} {of}\mspace{14mu} {glycoside}\mspace{14mu} {bonds}\mspace{14mu} {cleaved}}{{number}\mspace{14mu} {of}\mspace{14mu} {glycoside}\mspace{14mu} {bonds}\mspace{14mu} {in}{\mspace{11mu} \;}{the}\mspace{14mu} {starting}\mspace{14mu} {starch}} \right)}$

The dextrins in accordance with the invention can be obtained fromstarch or starch derivatives of varied plant origin, for exampleresulting from tubers, such as potato, cassava, maranta and sweetpotato, resulting from seeds, such as wheat, corn, rye, rice, barley,millet, oats and sorghum, resulting from fruit, such as horse chestnut,sweet chestnut and hazelnut, or resulting from leguminous plants, suchas peas and beans.

Preferably, the reducing sugar is chosen from glucose, polysaccharidescomposed predominantly (to more than 50% by weight) of glucose units andmixtures of these compounds.

The inorganic acid metal salt acts as inorganic acid precursor, whichacid reacts with the reducing sugar under the effect of the heat to forma polymeric network constituting the final binder. The polymeric networkthus formed makes it possible to establish bonds at the junction pointsof the fibers in the mineral wool.

As already indicated, the inorganic acid metal salt is chosen frominorganic acid alkali metal, alkaline earth metal, transition metal orpoor metal salts. Preferably, it is a sodium, magnesium, iron, cobalt,nickel, copper, zinc or aluminum salt, advantageously an aluminum orcopper salt.

The inorganic acid metal salt is advantageously chosen from sulfates,chlorides, nitrates, phosphates and carbonates and better still fromsulfates and chlorides.

Preference is given to aluminum sulfate, copper sulfate, potassiumaluminum sulfate (or potassium alum), iron sulfate, zinc sulfate andaluminum chloride, in particular to aluminum sulfate and copper sulfate.

In the sizing composition, the inorganic acid metal salt represents from1 to 30% by weight of the total weight of the mixture composed of thereducing sugar and the inorganic acid metal salt, preferably from 3 to20% and advantageously from 5 to 15%.

The sizing composition in accordance with the invention can alsocomprise the conventional additives below in the following proportions,calculated on the basis of 100 parts by weight of reducing sugar and ofinorganic acid metal salt:

-   from 0 to 2 parts of silane, in particular an aminosilane,-   from 0 to 20 parts of oil, preferably from 4 to 15 parts,-   from 0 to 20 parts of glycerol, preferably from 0 to 10 parts,-   from 0 to 5 parts of a silicone,-   from 0 to 30 parts of an “extender”.

The role of the additives is known and is briefly restated: the silaneis an agent for coupling between the fibers and the binder, and alsoacts as antiaging agent; the oils are dust-preventing and hydrophobicagents; the glycerol acts as plasticizer and makes it possible toprevent pregelling of the sizing composition; the silicone is ahydrophobic agent having the role of reducing the absorption of water bythe insulating product; the “extender” is an organic or inorganicfiller, soluble or dispersible in the aqueous sizing composition, whichmakes it possible in particular to reduce the cost of the sizingcomposition.

The sizing composition exhibits a pH which varies to a large extentaccording to the nature of the inorganic acid metal salt used, generallyfrom 2 to 10, advantageously acidic, in particular of less than or equalto 5.

The sizing composition is intended to be applied to mineral fibers, inparticular glass or rock fibers.

Conventionally, the sizing composition is projected onto the mineralfibers at the outlet of the centrifugal device and before they arecollected on the receiving member in the form of a web of fibers whichis subsequently treated at a temperature which makes possible thecrosslinking of the size and the formation of an infusible binder. Thecrosslinking of the size according to the invention takes place at atemperature of the order of from 100 to 200° C., generally at atemperature comparable to that of a conventional formaldehyde-phenolresin, in particular of greater than or equal to 110° C., preferably ofless than or equal to 170° C.

The acoustic and/or thermal insulating products obtained from thesesized fibers also constitute a subject matter of the present invention.

These products are generally provided in the form of a mat or felt ofmineral wool, of glass or of rock, or of a veil of mineral fibers, alsoof glass or of rock, intended in particular to form a surface coating onsaid mat or said felt.

The following examples make it possible to illustrate the inventionwithout, however, limiting it.

In these examples, the following are measured:

-   the crosslinking start temperature (T_(C)) and the crosslinking    rate (R) by the Dynamic Mechanical Analysis (DMA) method, which    makes it possible to characterize the viscoelastic behavior of a    polymeric material. The procedure is as follows: a sample of Whatman    paper is impregnated with the sizing composition (content of organic    solids of the order of 40%) and is then fixed horizontally between    two jaws. An oscillating component equipped with a device for    measuring the stress as a function of the strain applied is    positioned on the upper face of the sample. The device makes it    possible to calculate the modulus of elasticity E′. The sample is    heated to a temperature varying from 20 to 250° C. at the rate of 4°    C./min. The curve of variation in the modulus of elasticity E′ (in    MPa) as a function of the temperature (in ° C.) is plotted from the    measurements, the general appearance of the curve being given in    FIG. 1. The values corresponding to the crosslinking start    temperature (T_(C)), in ° C., and the slope corresponding to the    crosslinking rate (R), in MPa/° C., are determined on the curve.-   the viscosity, expressed in mPa.s, using a rheometer of plate/plate    rotational type with shearing of 100 s⁻¹ at 25° C. The sample has a    solids content of 30% by weight.-   the contact angle of the sizing composition on a glass substrate.-   the tensile strength according to the standard ASTM C 686-71T on a    sample cut out by stamping from the insulating product. The sample    has the shape of a torus with a length of 122 mm, a width of 46 mm,    a radius of curvature of the cut-out of the outer edge equal to 38    mm and a radius of curvature of the cut-out of the inner edge equal    to 12.5 mm.

The sample is positioned between two cylindrical mandrels of a testmachine, one of which is movable and is moved at a constant rate. Thebreaking force F (in gram-force) of the sample is measured and thetensile strength TS, defined by the ratio of the breaking force F to theweight of the sample, is calculated.

The tensile strength is measured after manufacture (initial tensilestrength) and after accelerated aging in an autoclave at a temperatureof 105° C. under 100% relative humidity for 15 minutes (TS 15).

-   the initial thickness of the insulating product and the thickness    after compressing for 1 hour, 24 hours and 30 days with a degree of    compression (defined as being the ratio of the nominal thickness to    the thickness under compression) equal to 4.8/1. The thickness    measurements make it possible to evaluate the good dimensional    behavior of the product.-   the thermal conductivity coefficient λ according to the standard EN    13162, expressed in W/(m×° K).

EXAMPLES 1 TO 8

Sizing compositions are prepared which comprise the constituentsappearing in Table 1, expressed as parts by weight.

The sizing compositions are prepared by successively introducing, into avessel containing water, the reducing sugar and the inorganic acid metalsalt with vigorous stirring until the constituents have completelydissolved.

The following dextrins are used as reducing sugar:

-   glucose syrup 74/968®, which has a glucose content by weight of    greater than 95% and exhibits a dextrose equivalent DE equal to 99    (sold by Roquette Frères; solids content: 75%);-   Flolys® B6080S, which has a weight-average molar mass of 1520 and a    dextrose equivalent DE of 62 (sold under the reference by Roquette    Frères; solids content: 81%).

The properties of the sizing compositions which appear in table 1 areevaluated in comparison with a conventional sizing composition includinga formaldehyde-phenol resin and urea (Reference) prepared in accordancewith example 2, test 1, of WO 01/96254 A1 and with a compositioncomprising only the reducing sugar (C1).

The sizing compositions of examples 1 to 8 exhibit a crosslinking starttemperature (T_(C)) which is lower than that of the Reference. Thesecompositions also exhibit a crosslinking rate (R) close to that of theReference, and even significantly higher (examples 2 and 3).

The sizing compositions of examples 1 to 8 additionally have a lowviscosity, lower than that of the Reference at an identical solidscontent, which allows good application to the mineral fibers, inparticular by spraying.

The sizing compositions according to the invention also exhibit a lowcontact angle on a glass substrate, which denotes a good ability to wetthe fibers.

EXAMPLE 9

This example illustrates the manufacture of insulating products on anindustrial line.

A sizing composition is prepared which comprises the followingconstituents (as parts by weight):

glucose syrup 74/968 ® 92.5 aluminum sulfate 7.5γ-aminopropyltriethoxysilane 1.0 mineral oil 8.0 silicone 1.5

Glass wool is manufactured by the internal centrifugation technique inwhich the molten glass composition is converted into fibers by means ofa tool, referred to as centrifuging disk, comprising a basket forming achamber for receiving the molten composition and a peripheral bandpierced by a multitude of orifices: the disk is rotated about itsvertically positioned axis of symmetry, the composition is ejectedthrough the orifices under the effect of the centrifugal force and thematerial escaping from the orifices is drawn into fibers with theassistance of a drawing gas stream.

Conventionally, a size spraying ring is positioned beneath thefiberizing disk so as to uniformly distribute the sizing compositionover the glass wool which has just been formed.

The mineral wool, thus sized, is collected on a belt conveyor with awidth of 2.4 m equipped with internal extraction boxes which hold themineral wool in the form of a web at the surface of the conveyor. Theweb passes continuously through an oven maintained at 270° C., where theconstituents of the size polymerize to form a binder. The finalinsulating product has a density of 17.5 kg/m³.

During the manufacture of the insulating product, the nitrogen emissionsin the chimney remained at a minimal level.

The insulating product exhibits the following properties:

Tensile strength (gf/g) before aging 206 after aging 150 loss (%) 27Thickness (mm) after 1 hour 83.5 after 24 hours 81.6 after 30 days 79.5Loss on ignition (%) 6.0 λ (W/(m × ° K)) 0.035

The insulating product is stable in thickness and retains mechanicalcohesion after aging. This product can be used in particular inapplications where the mechanical stress is relatively unimportant, forexample for the insulation of unoccupied attics.

EXAMPLES 10 TO 14

These examples illustrate the manufacture of insulating products in anindustrial plant employing different inorganic acid metal salts.

The procedure is carried out under the conditions of example 9, modifiedin that, in the sizing compositions, the glucose syrup 74/968® and theinorganic acid metal salts are present in the proportions shown in table2 (as parts by weight).

The properties of the insulating products obtained are collated in table2.

TABLE 1 Example 1 2 3 4 5 6 7 8 C1 Reference Sizing Composition Reducingsugar Glucose syrup 74/968 ® 95 90 — 92.5 85 85 92.5 85 100 — Flolys ®BS6080S — — 85 — — — — — — — Inorganic acid metal salt Aluminum sulfate 5 10 15 — — — — — — — Copper sulfate — — —  7.5 15 — — — — — Potassiumalum — — — — — 15 — — — — Aluminum chloride — — — — — —  7.5 15 — —Properties Crosslinking start temp. T_(c) (° C.) 122 115 102 126 119 121116 110 234 151 Crosslinking rate R (MPa/° C.) 128 293 345 100 150 163141 129 16 161 Viscosity at 25° C. (mPa · s)⁽¹⁾ 6.4 6.5 7.0 5.8 6.1 6.46.3 6.7 6.1 8.0 Contact angle (°)⁽²⁾ 28 16 30 32 31 28 32 33 27 10.0 pH2.9 2.8 2.8 3.2 3.1 2.8 2.4 2.2 3.6 6.0 ⁽¹⁾solution with a solidscontent of 30% ⁽²⁾solution with a solids content of 40%

TABLE 2 Example 10 11 12 13 14 Sizing composition Glucose syrup 74/968 ®85 92.5 85 85 85 Aluminum sulfate 15 — — — — Copper sulfate — 7.5 15 — —Iron(II) sulfate — — — 15 — Zinc sulfate — — — — 15 Properties Tensilestrength (gf/g) before aging 192 188 224 144 167 after aging 168 238 241159 174 loss 12.5% −26.5% −7.5% −10.4% −4.1% Thickness (mm)  1 hour 80.585.6 84.2 89.5 90.2 24 hours 79.2 83.6 81.7 86.0 87.8 30 days 76.3 81.578.6 84.6 87.9 Loss on ignition (%) 5.5 5.5 5.5 5.5 5.5 λ (W/(m × ° K))0.035 0.035 0.035 0.035 0.035

1. A sizing composition for insulating products based on mineral wool,in particular of rock or of glass, the composition comprising: at leastone reducing sugar, and at least one inorganic acid metal salt chosenfrom inorganic acid alkali metal, alkaline earth metal, transition metalor poor metal salts.
 2. The composition as claimed in claim 1, whereinthe reducing sugar is a monosaccharide, an oligosaccharide, apolysaccharide or a mixture of these compounds.
 3. The composition asclaimed in claim 2, wherein the reducing sugar is glucose, galactose,mannose, fructose, lactose, maltose, isomaltose, cellobiose or adextrin.
 4. The composition as claimed in claim 1, wherein the reducingsugar is chosen from glucose, polysaccharides comprising more than 50%by weight of glucose units and mixtures of these compounds.
 5. Thecomposition as claimed in claim 1, wherein the inorganic acid metal saltis a sodium, magnesium, iron, cobalt, nickel, copper, zinc or aluminumsalt, preferably an aluminum or copper salt.
 6. The composition asclaimed in claim 5, wherein the inorganic acid metal salt is chosen fromsulfates, chlorides, nitrates, phosphates and carbonates, preferablysulfates and chlorides.
 7. The composition as claimed in claim 5,wherein the inorganic acid metal salt is aluminum sulfate, coppersulfate, potassium aluminum sulfate (or potassium alum), iron sulfate,zinc sulfate and aluminum chloride, preferably aluminum sulfate andcopper sulfate.
 8. The composition as claimed in claim 1, wherein theinorganic acid metal salt represents from 1 to 30% by weight of thetotal weight of the mixture composed of the reducing sugar and theinorganic acid metal salt, preferably from 3 to 20% and advantageouslyfrom 5 to 15%.
 9. The composition as claimed in claim 1, comprising theadditives below in the following proportions, calculated on the basis of100 parts by weight of reducing sugar and of inorganic acid metal salt:from 0 to 2 parts of silane, in particular an aminosilane, from 0 to 20parts of oil, preferably from 4 to 15 parts, from 0 to 20 parts ofglycerol, preferably from 0 to 10 parts, from 0 to 5 parts of asilicone, from 0 to 30 parts of an “extender”.
 10. An acoustic and/orthermal insulating product based on mineral wool, in particular of glassor of rock, sized using the sizing composition as claimed in claim 1.11. A veil of mineral fibers, in particular of glass or of rock, sizedusing the sizing composition as claimed in claim
 1. 12. A process forthe manufacture of an acoustic and/or thermal insulating product basedon mineral wool or of a veil of mineral fibers, the method comprising:projecting a sizing composition onto said wool or said fibers, andtreating said wool or said fibers at a temperature which makes possiblethe crosslinking of the size and the formation of an infusible binder,wherein the sizing composition comprises: at least one reducing sugar,and at least one inorganic acid metal salt chosen from inorganic acidalkali metal, alkaline earth metal, transition metal or poor metalsalts.